Parent key and child keys
In the tables, it is possible to distinguish the child keys and the parent key.
All keys to the right of a given key, in the same row and in the next column, are called child keys of a parent key. Thus, the given key is called the parent key.

All keys below the given key, in the same column and in the next row, are called child keys of the parent key. Thus, the given key is called the parent key.

See also
Selecting cells and keys in a table, copying and pasting values